[Simh] PDP-10 DECtapes

[Timothe Litt]

Good information, but this thread is about DECtape, not 9-Track magtapes...

The format looks about right for 9-track DOS-11 magtapes; I remember 
writing code to extract files from them on the -10.

It's not right (or at least, not complete) for the block-addressable 
DECtapes.

I don't think DOS-11 would have been documented in any of the references 
cited.

There's now a SIMH repo on github; your utility could go into the tools 
section.

This communication may not represent my employer's views,
if any, on the matters discussed.

On 28-Mar-13 14:09, Larry Baker wrote:
> On 28 Mar 2013, at 5:24 AM, <simh-request at trailing-edge.com 
> <mailto:simh-request at trailing-edge.com>> 
> <simh-request at trailing-edge.com 
> <mailto:simh-request at trailing-edge.com>> wrote:
>
>> Google 'AA-JS16A-TC' for some Files-11 format information; I'd
>> have to think a bit on the DOS-11 format.
>
> RSX/VMS Files-11 tapes are ANSI labeled tapes.  I know OpenVMS also 
> used HDR3/4 labels for RMS information.  There was a MOUNT option to 
> suppress writing those labels.
>
> I wrote an RSX/VMS  program that will scan an unknown tape and decode 
> it for you.  (If anyone wants it, let me know where I should upload 
> it.)  The DOS format decoder looks for a 14 byte (physical) record at 
> the start of the file.  It is decoded by the following code:
>
> C
> C...  DEC DOS labels
> C
>       Call R50ASC ( 6, buffer( 1), ascbuf( 1) )
>       Call R50ASC ( 3, buffer(13), ascbuf( 7) )
>       ascbuf(10) = '.'
>       Call R50ASC ( 3, buffer( 5), ascbuf(11) )
>       ltemp(1) = buffer(7)
>       ltemp(2) = 0
>       mem = itemp
>       ltemp(1) = buffer(8)
>       grp = itemp
>       ltemp(1) = buffer(11)
>       ltemp(2) = buffer(12)
>       jday = MOD(itemp,1000)
>       year = itemp/1000 + 70
>       Call JDCONV ( jday, mon, day, year )
>       ltemp(1) = buffer( 9)
>       ltemp(2) = buffer(10)
>       Write (STDOUT,619) ifile, grp, mem, ascbuf, day, month(mon),
>      1                   year, itemp
>   619 Format (//' File ', I4, ':', T34, '"', '[', O3.3, ',', O3.3, ']',
>      1        13A1, 2X, I2, '-', A, '-', I2.2, '  <', O3.3, '>', '"')
>
> The DOS label contents are:
>
> Words 1-2 RAD50 characters 1-6 of the file name part (before the 
> implied period)
> Word 3 RAD50 characters 1-3 of the file type (after the implied period)
> Word 4 Octal File owner's User Identification Code (group code in 
> high-order byte, member code in low-order byte)
> Word 5 Binary File creation date ( 1000 * ( year - 1970 ) + Julian day )
> Word 6 Octal File protection (low-order to high-order RWED bits: read, 
> write, extend, delete; grouped low-order to high-order for system, 
> owner, group, world)
> Word 7 RAD50 characters 7-9 of the file name part (before the implied 
> period)
>
> The references I used to write the program (back in the 1980's) are 
> below.  Which reference had the DOS label format I don't remember (if 
> any of them did).
>
> 6  References
>
> [1]  American National Standards Institute, 1978, Magnetic Tape Labels
>      and File Structure for Information Interchange (ANSI X3.27-1978).
>
> [2]  Digital Equipment  Corp.,  1985,  RSX-11M/M-Plus  MCR  Operations
>      Manual (Order no. AA-FD10A-TC).
>
> [3]  Digital Equipment  Corp.,  1985,  RSX-11M-Plus  Command  Language
>      Manual (Order no. AA-FD04A-TC).
>
> [4]  Digital Equipment Corp., 1985, RSX-11M/M-Plus and  Micro/RSX  I/O
>      Operations Reference Manual (Order no. AA-FD14A-TC).
>
> [5]  Digital  Equipment  Corp.,  1985,  RSX-11M/M-Plus I/O   Drivers
>      Reference Manual (Order no. AA-FD09A-TC).
>
> [6]  Digital Equipment Corp., 1984, VAX/VMS Command Definition Utility
>      Reference Manual (Order no. AA-Z408A-TE).
>
> [7]  Digital Equipment Corp., 1986, VAX/VMS DCL Dictionary (Order  no.
>      AA-Z200C-TE).
>
> [8]  Digital Equipment Corp., 1984, VAX/VMS  Mount  Utility  Reference
>      Manual (Order no. AA-Z424C-TE).
>
> [9]  Digital Equipment Corp., 1986, Guide to VAX/VMS Disk and Magnetic
>      Tape Operations (Order no. AI-Y506B-TE).
>
> [10] Digital Equipment  Corp.,  1986,  VAX/VMS  I/O  User's  Reference
>      Manual:  Part I (Order no. AA-Z600C-TE).
>
> [11] International Business Machines Corp., 1978,  OS/VS  Tape  Labels
>      (Order No. GC26-3795-1).
>
> Larry Baker
> US Geological Survey
> 650-329-5608
> baker at usgs.gov <mailto:baker at usgs.gov>
>
>
> _______________________________________________
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> Simh at trailing-edge.com
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